The present invention relates to a control apparatus and a control method of an automatic transmission for a vehicle, for setting a shift point based on grade resistance of a running road surface.
In such an apparatus, when a brake operation (braking) is performed where there is caused an error in an estimation value of grade resistance, the shift point is set based on the grade resistance estimated before the brake operation.
In the conventional technique as described above, if a brake is operated during down-slope running, update of the estimation value of grade resistance is stopped.
Consequently, even in a case where a decline becomes steeper during the brake operation, leading a condition that a forcible downshift should be essentially performed, the shift point is determined on the basis of a comparatively gentle decline before the brake operation. As a result, there is caused a problem in that an appropriate downshift cannot be performed.
Therefore, the present invention has an object to enable to obtain an estimation result closer to actual grade resistance even when braking is performed where there is caused an error in an estimation value of grade resistance, thereby setting a more appropriate shift point.
In order to achieve the above object, the present invention has a constitution in that, when vehicle braking is performed, a minimum value of grade resistance calculated based on operating conditions of a vehicle is held, to set a shift point based on the held minimum value.
The other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.